1. Field of the Invention
The present invention relates to a display apparatus, in particular a display apparatus equipped with a brightness sensor for measuring brightness of light from a backlight unit.
2. Description of Related Art
Conventionally, a liquid crystal display apparatus that utilizes a change in optical property of liquid crystal for display is known as a display apparatus. Such a liquid crystal display apparatus is provided with a backlight unit disposed on the rear side of the liquid crystal display panel, and light emitted from the backlight unit irradiates the liquid crystal display panel so that characters and images can be displayed. In addition, there is known a conventional technique for adjusting brightness of light emitted from the backlight unit by using data measured by a brightness sensor (see JP-A-2000-315596, for example).
The above mentioned document JP-A-2000-315596 (hereinafter referred to as a “conventional technique”) discloses a structure of a backlight unit including a brightness sensor that delivers a brightness measured signal to a control device (not shown) via a lead wire and is fixed to an opening portion disposed on the rear side of a casing that houses a lamp and a light guide as shown in FIG. 1 of the conventional technique. In addition, the above mentioned conventional technique also discloses a structure of a backlight unit in which an attachment member is disposed on the rear side of the casing, and a brightness sensor is attached to a surface of the attachment member that is closer to the backlight case as shown in FIG. 3 of the conventional technique. Furthermore, in the example shown in FIG. 1 of the above mentioned conventional technique, the lead wire of the brightness sensor is drawn out to the rear side of the backlight unit. Therefore, it is considered that the control device (not shown) of the liquid crystal display apparatus is connected to the brightness sensor electrically via the lead wire of the brightness sensor.
However, the structure shown in FIG. 1 of the above mentioned conventional technique does not clarify a method of fixing the brightness sensor, and there is a problem that this fixing method needs a component. In addition, the conventional technique does not clarify also a method of connecting the lead wire, and there is a problem that a connector or a manual work of soldering is necessary. In addition, there is also a problem that the brightness sensor may be affected largely by temperature if it is attached directly to the casing because brightness detection output of the brightness sensor varies in accordance with temperature. Furthermore, the structure disclosed in the above mentioned conventional technique needs a space for routing the lead wire of the brightness sensor, so there is a problem that it becomes difficult to downsize the display apparatus.
The structure disclosed in the example shown in FIG. 3 of the above mentioned conventional technique has a problem that thickness of the backlight unit increases because the brightness sensor is attached to a surface of the attachment member that is closer to the backlight case. Although the conventional technique does not disclose, if a control circuit board that is connected to the display panel is used as the attachment member too, the surface opposite to the surface on which the brightness sensor is attached as the example shown in FIG. 3 of the conventional technique becomes a component side for a reason of assembling matter, because a flexible printed circuit board for a gate driver and a flexible printed circuit board for a source driver that extend in directions perpendicular to each other are connected to the control circuit board. For this reason, even if the control circuit board that is connected to the display panel is also used as the attachment member, thickness of the backlight unit increases. In addition, the work of attaching the brightness sensor onto the surface that is opposite to the normal component side will become difficult. Further, there is a problem that brightness detection output of the brightness sensor is affected largely by temperature because the brightness sensor is close to the casing that becomes high temperature.